Hey all, I have a bbc 468 did all myself I mean built all myself, and I go to put it in my 74 c20 truck and have had problems with the starter grinding and chewing up my flexplate I shimmed till it worked but you shouldnt have to shim that much. So bought a new starter hitachi high cranking starter and had more problems with that then the first so i just put in the stock one and lived with the shim for now.But every now and then it grinds until i tap it slow so it meshes back up. Come to find after doing research on the site and some serious brainstorming and found out my hitachi is 153 and 168 it fits both sizes and it bolts up straight across. My stock starter bolts up staggered so does the straight and staggered bolt pattern have to do with what size the flexplate is, and if so back to the original question which is better 153 or 168 and why do they use both sizes.I got a new flexplate thats the same size as what I have now which i think and pretty sure its 168. Since I have new plate and starter going to buy new bolts just to be safe so I have new evrything thats has to to with starter or starting. Thanks all.